Express.js File Upload

Introduction to Express.js File Upload

In Express.js, file upload is the process of transferring files from a client (usually a web browser) to a server. The uploaded files can be images, videos, documents, or any other type of file. To handle file uploads in Express.js, you can use middleware such as Multer, a Node.js middleware used for handling multipart/form-data, which is mainly used for file uploads.

Multer provides various options for handling file uploads, such as specifying the upload directory, setting the file size limit, and filtering files based on their type. Multer is used in express js to fetch the data from the uploaded express file. Multer generates the req. file object, which includes all of the information about the uploaded file.

Formidable is another popular middleware for handling file uploads in Express.js. It supports streaming large files and has options for setting the file size limit, defining the upload directory, and specifying the file type.

Express-fileupload

Now, let’s discuss the express-file upload installation, USA, age and options.

Install

There are two ways to install the ``express-fileupfile upload* Using NPM

• Using Yarn

Usage

When a user uploads a file on a server using express then the user can access the file using req.files as an object for the file.

Let’s understand it with the help of an example:- We are uploading a file named express upload file.jpeg. We can access the uploaded file from req.files.temp (temp is the file input name) in the express server request.

Here's an example of how to access the uploaded file in Express.js:

In the code above, we define a route to handle file uploads using the upload.single() method. When a file is uploaded, the req.file object is filled with details about it.

We then check if req.file exists and return an error message if it doesn't. If req.file exists, we can access information about the uploaded file using req.file. In this example, we simply send a success message back to the client, but you can use req.file to process the file or save it to a database.

Note that if you're uploading multiple files, you can access them using req.files, which is an array of files.

Options

Busboy is a Node.js module used for handling express upload files, which can be used as an alternative to Multer in Express.js. Busboy is a streaming parser for parsing form data from HTTP requests, including file uploads.

Here's an illustration of how to use Express.js's Busboy to manage file transfers:

In the code above, we define a route to handle file uploads using Busboy. We create a new instance of Busboy and pass the request headers to it. We then listen for the file event, which is emitted for each file upload.

When a file is uploaded, we can access its metadata, such as the fieldname, filename, encoding, and mimetype. We then handle the file stream using the file object, which is a Readable stream.

We listen for the data and end events on the file stream, which allow us to process the file data as it's being uploaded. In this example, we simply log the number of bytes received and when the upload is complete.

When all files have been uploaded, we listen for the finish event on Busboy, which is emitted when the request stream has been completely parsed.

Use Express-fileupload to Handle Uploading Files

Below are the steps which help to understand how to handle the express uploading files.

• Install the express-fileupload module:-

• Require the express-fileupload middleware in your Express.js app:-

• Enable file upload middleware

• Define a route to handle file uploads:

In the code above, we first enable the express-fileupload middleware by calling app.use(fileUpload()). This adds a req.files object to the request, which contains information about the uploaded files.

Next, we define a route to handle file uploads. We first check if files were uploaded by checking if req.files exists and is not empty. If no files were uploaded, we return a 400 Bad Request status code.

If files were uploaded, we access the uploaded file by referencing its field name in the req.files object. In this example, we assume the uploaded file has a field name of myFile.

Finally, we move the uploaded file to the desired location using the mv method of the file object. We specify the destination path and filename in the first argument of mv, and provide a callback function that will be called when the file has been moved. If there's an error moving the file, we return a 500 Internal Server Error status code. Otherwise, we send a success message back to the client.

Note that you can customise the behaviour of express-fileupload using various options. For example, you can specify the maximum file size, the allowed file types, and the destination directory for uploaded files.